The invention relates to a method as recited in the preamble of claim 1. The art of data storage and transmission has recognized the advantages of data compression. A particularly advantageous compression scheme has been to conceptually replace a particular data string by an earlier occurrence of an unencoded, or rather decoded, data string that has exactly the same content. The signalling of such replacing is formulated as a relative pointer combined with an indication of the length of the replacing string. Now, a pointer-length pair will often have a greater length than a standard length character. At a subsequent decoding operation, this scheme will therefore necessitate a buffer for storing all earlier decoded information within the range of the pointer to allow the resolving of all back-references. Practical embedded systems will however often feature a scarcity in available RAM storage space that would serve as such buffer. This may imply an unacceptable cost level, or may even defeat the applying of this technology.
In consequence, amongst other things, it is an object of the present invention to allow diminishing the requirements for RAM storage space. Now, the present inventor has recognized a procedure that would realize an appreciable advantage by having the pointers referring back to earlier encoded objects or strings. One argument in case is that ROM storage will generally be amply available for storing encoded data, such as would be the case in many embedded systems. However, the above storage-related argument is not a prerequisite for attaining the various advantages of implementing the invention. The improved scheme will by and large obviate the need for buffering decoded data, and furthermore will allow for a certain amount of random accessibility. The invention especially envisages its application in relatively inexpensive appliances. In various situations, the invention will also allow for a higher compression factor. Furthermore, a pointer will often span multiple objects, that may include both original versions and pointer-length pairs, rather than only characters or other standard-length items. With the same pointer size, this feature allows using a larger pointing range and therefore, an improved compression rate. On the other hand, through keeping the same pointing range as before, the present invention will allow to use shorter pointers, and in consequence, will realize an improved compression rate as well. Trade-offs will likewise represent fortuitous implementations of the present invention.
Now therefore, according to one of its aspects the invention is characterized according to the characterizing part of Claim 1.
The invention also relates to a system for implementing a method as claimed in Claim 1, to an encoding device and to a decoding device arranged for implementing a method as claimed in Claim 1, and to a storage medium provided with information produced by such encoding device and/or arranged for decoding by such decoding device. Further advantageous aspects of the invention are recited in dependent claims.